   stateful transducer when no collection is provided."
   ([pred]
      (fn [rf]
-       (let [da (atom true)]
+       (let [da (volatile! true)]
          (fn
            ([] (rf))
            ([result] (rf result))

  transducer when no collection is provided."
  ([n]
     (fn [rf]
       (let [ia (atom -1)]
         (fn
           ([] (rf))
           ([result] (rf result))
           ([result input]
              (let [i (swap! ia inc)]
                (if (zero? (rem i n))
                  (rf result input)
                  result)))))))

  Returns a transducer when no collection is provided."
  ([]
   (fn [rf]
     (let [pa (volatile! ::none)]
       (fn
         ([] (rf))
         ([result] (rf result))
         ([result input]
            (let [prior @pa]
              (vreset! pa input)
              (if (= prior input)
                result
                (rf result input))))))))
